The hydroesterification of olefins by reaction with carbon monoxide and alcohols, utilizing cobalt catalyst in the presence of pyridine, is a known process. However, various problems have been encountered in attempting to conduct the process under conditions for good catalyst stability and efficiency, good reaction rates and product selectivity, along with effective product recovery and catalyst recycle procedures. Low catalyst concentrations have generally been used because of concern over catalyst stability. Also relatively high pressures have often been employed to effect the reaction and enhance catalyst stability. Some described procedures have unacceptable reaction rates, particularly for internal olefin reactants which are less reactive. The procedures often emphasize .alpha.-olefin reactants, perhaps because of the tendency of internal olefins to produce branched products rather than linear products which are generally more desirable. There was some belief that normality of the ester increased with declining temperature and rising carbon monoxide pressure.
Problems have also been encountered in catalyst recovery or recycling. It is desirable to recycle the cobalt as a matter of efficiency and economics. In addition, cobalt when present causes difficulties in distillation of product, causing formation of high boiler material, and also often plating out in distillation apparatus. Conditions to improve catalyst recovery often have poor compatibility with conditions for effective reaction, or which are considered appropriate for catalyst stability during reaction.
While prior procedures set forth various conditions, they do not describe conditions including combinations of temperature, pressure and cobalt concentration suitable for achieving good reaction rate and high normal content of ester product, along with catalyst stability and recoverability.